6o6 THE POPULAR SCIENCE MONTHLY. 



peared to be volcanic hyjDersthene, pyroxene, magnetic iron, and vol- 

 canic glass. At Wageningen, every drop of the rain that fell upon 

 the windows left, when it dried up, a slight sediment of grayish- 

 colored matter which was compared with original volcanic ash from 

 Krakatoa that had been sent to the Agricultural Laboratory for analy- 

 sis. Both the sediment and the volcanic ash were found to contain in 

 common — 1. Small, transparent, glassy particles ; 2. Brownish, half- 

 transparent, somewhat filamentous little staves ; and, 3. Jet-black, 

 sharp-edged, small grains resembling augite. These observations, say 

 Messrs. Beyerinck and Van Dam, who made the analyses, *' fortify us 

 in our supposition that the ashes of Krakatoa have come down in Hol- 

 land." On the 17th of November a fall of layers of gray and black 

 dust took place at Storlvdal, Norway, and a fall of discolored rain 

 near Worcester, England. Grayish sediments were found deposited 

 on windows at Gainsborough and York, England, after a heavy rain 

 on the 12th of December. 



Mr. E. Douglas Archibald has suggested in " Nature " that, whether 

 the cause of the phenomena be meteoric dust or volcanic ashes, the re- 

 flection arises from a definite stratum, and not merely from an atmos- 

 phere filled throughout with such dust. Professor Roujon, of Cler- 

 mont, France, has also observed that two of the twilights, one following 

 the other one day apart, " were so different in intensity as to provoke 

 the supposition that the substance which produced them, at a great 

 height, was not uniformly diffused, but moved in vast masses." This 

 would serve to account for the variations that all must have observed 

 in the brilliancy of the glow. 



Mr. Edmund Clark has offered a suggestion upon which the theory 

 that invokes the agency of aqueous vapor and the one which refers 

 the manifestations to volcanic or meteoric dust may be combined, viz., 

 that the dust may act as a nucleus for the condensation of any vapor 

 that may exist at such a high level. The height of the mass of the 

 matter producing the glow has been fixed by Miss Ley, of England, 

 at thirteen miles. 



THE ANCESTEY OF BIEDS. 



By Peofessob GEANT ALLEN. 



SEATED on the dry hill-side here, by the belted blue Mediterranean, 

 I have picked up from the ground a bit of blanched and molder- 

 ing bone, well cleaned to my hand by the unconscious friendliness of 

 the busy ants ; and looking closely at it I recognize it at once, with 

 a sympathetic sigh, for the solid welded tail-piece of some departed 

 British tourist swallow. He came here like ourselves, no doubt, to 

 escape the terrors of an English winter : but among these pine-clad 



